Dual-drum dryer

ABSTRACT

A dual-drum rotating dryer having an annular passageway between the drums through which the material being dried is caused to pass as it progresses through the dryer, the dryer being comprised of an outer drum and an inner drum positioned therein.

United States Patent Qulles [4 July 25, 1972 DUAL-DRUM DRYER [56] References Cited [72] Inventor: Francisco K. Quiles, Salamanca, UNITED STATES PATENTS Guanajuato, Mexico 423,670 3/1890 Charnock ..34/134 1,431,037 10/1922 Prindle [73] Assgnee' 2,410,675 11/1946 Nichols..... ..34/134 x 221 Filed: June 19, 1970 Primary ExaminerCarroll B. Dority, Jr. [21] App1.No.: 47,253 AttarneyYoung and Quigg 57 ABSTRACT [52] US. Cl. ,.34/l28, 34/134, 263/32 R 1 51 1111.01 ..F26b 11/02 A dual-drum rotating dryer having an annular passageway [58] Field ofSearch ..34/128 132 134 137- betwee" the drums hwugh which material being dried is 5 R caused to pass as it progresses through the dryer, the dryer WET PELLETS being comprised of an outer drum and an inner drum positioned therein.

5 Claims, 3 Drawing Figures DRY PELLETS PATENTEDJUL 25 I972 3. 678 59 8 WET PELLETS DRY PELLETS INVENTOR.

FRANCISCO K.QUILES ATTORNEYS DUAL-DRUM DRYER This invention relates to a rotating drum dryer.

In one of its more specific aspects, this invention relates to a dual-drum rotary dryer which has a greater drying capacity than conventional single-drumrotary dryers.

The use of single-drum rotary dryers is well known. Generally, these comprise a horizontally disposed drum through which solids are passed with a tumbling action as the drum rotates. The solids are dried upon travelling the length of the drum in contact with a surface of the drum which can be heated in a number of ways. In one type, heat is supplied from the outside of the drum to the inner surface of the drum with which the solids come in contact. In some types, heat is supplied by passing a hot gas through the drum, preferably in a direction countercurrent to the general direction of flow of solids through the drum.

There has now been developed a rotary drum dryer of greater capacity than that of conventional single-drum dryers. The apparatus of this invention provides such a dryer which comprises an outer chamber adapted for rotation about its longitudinal axis, this outer chamber being adapted at one end for the introduction of particulate matter onto its inner surface, the chamber being adapted at its second and opposite end for the discharge of the particulate matter, an inner chamber positioned within the outer chamber and in spaced relationship to the inner wall of the outer chamber to form an annular passageway between the inner wall of the outer chamber and the outer wall of the inner chamber, the inner chamber being closed at its first end and adapted for introduction of gases at its second end, the inside of the inner chamber being in opencommunication with the annular passageway, means for introducing hot gases into the inner chamber and means for rotating the outer chamber.

Accordingly, it is an object of this invention to provide a dryer of increased capacity.

It is also an object of this invention to provide a dryer in which the attrition of the particles being dried is less than that which occurs in conventional dryers.

In general, the apparatus of the present invention comprises a dual-drum dryer in which an inner drum or chamber is positioned, either slidably, or affixed, within an outer drum or chamber. The material to be dried is introduced in the annular passageway between the drums so as to contact both the outer surface of the inner drum and the inner surface of the outer drum.

The hot gases introduced into the inner drum pass in contact with its inner surface and then pass into the annular passagewaybetween the two drums countercurrent to, and in direct contact with, the material passing through the annular passageway. Accordingly, the material being dried is contacted by surfaces which have been heated by the hot gases and is also contacted by the hot gases. Hence, extensive contact is effected between the hot gases, the surfaces which they heat, and the material being dried. Also, because of the attachments of vanes to the inner surface of the outer drum, a greater degree of contact is effected between the material to be dried and those hot drum surfaces which effect the drying. As a result, the dryer of the present invention has a capacity of at least ten percent greater than that of conventional dryers.

In one embodiment of this invention, three of the four longitudinal surfaces of the two drums are heated.

In a second embodiment of this invention, each longitudinal surface of both drums is heated.

While the apparatus of this invention will be described as employed for the drying of pelleted carbon black, it is not to be considered as being so limited.

The apparatus of this invention will be more easily understood if explained by reference to the attached drawings in which FIG. 1 illustrates a cross-sectional view in elevation of one embodiment of the apparatus of this invention, and

FIG. 2 illustrates a cross-sectional view in elevation taken through section 2-2 of FIG. 1;

FIG. 3 illustrates another embodiment of the invention.

Referring now to FIG. I, there is shown dryer 1 comprised of outer drum I0 and inner drurn II. Outer drum I0 is adapted for rotation around its longitudinal axis by any suitable means, not shown as item 35.

Outer drum 10 is open at its ends 4 and 5. It is equipped along at least a portion of its length with a plurality of vanes 12. These vanes are spaced around the inner wall of drum 10, as shown in FIG. 2 and provide unobstructed passageways 7 from open end 4 to open end 5. These vanes will be positioned at an angle of about 30 from the perpendicular.

The inner drum is positioned with its longitudinal axis parallei to that of the outer drum. It is positioned to ride within the outer drum, being supported within the outer drum by those vanes which have rotated tothe lowermost position 27 during the rotation of the outer drum. Such an arrangement is discussed hereinafter. The inner drum is positioned in spaced relationship from a principal portion of the length of those vanes at the uppermost position 18. This positioning provides space for passage for the material being dried between the top of the inner drum and the near edge of the vane affixed to the outer drum.

The inner drum is open at its end 19 but is closed at its opposite end by wall 15 which may conveniently be adapted with manhole 14. The interior of the inner drum I1 is in open communication with passageways 7 by means of passageways 17 at its open end I9.

Outer drum I0 is adapted at its end 4 for the introduction of carbon black into entry section 20.. When so introduced, because the dryer is operated in a slightly inclined position, the carbon black will pass along annular passageways 7 and leave the dryer through open end 5.

Because outer drum 10 is adapted for rotation, carbon black progressing along the length of the dryer through passageways 7 is carried upwardly by vanes 12 and into contact with the outer surface of the inner drum as the black progresses along the length of the dryer.

If the inner drum rides unaffixed to vanes 12, the inner drum will slide on the lower vanes with little or substantially no rotational motionbeing imparted to the inner drum. However, if desired, the inner drum can be affixed at points along its length to vanes 12 in which instance the inner drum will rotate in unison with the outer drum. This construction is shown in FIG. 3.

Referring now to FIG. 3 there is shown that embodiment in which the inner drum is affixed to the outer drum. As shown, outer drum 10 has vanes 12 affixed to its inner wall. These vanes, however, have projections 25 at one or more points along their length. One embodiment in which the projections are positioned at the ends of the vanes and at about the midpoint of the vane is indicated. These projections contact the outer surface of the inner drum. By affixing these projections to the outer surface of the inner drum, the inner drum is fixedly related to the outer drum and rotates coaxially with the outer drum.

That particulate matter being dried and which passes through passageways 7 will be elevated, as the drums rotate by those sections by those sections 27 of the vanes which are out of contact with the inner drum.

At some point in the rotation of the drums, that particulate matter will no longer be retained by vane sections 27 and will slide downward over the outer surface of the inner drum through those passageways 26 which exist between projections. In this construction, extensive contact between the material being dried and the hot gases or surfaces is effected.

Heat can be supplied to the dryer by any number of means. Generally, it will be supplied in the form of hot combustion gases. These gases can be introduced by any number of means into the inner drum, for example, as shown in FIG. I, by spider 24. These hot gases will preferably be introduced into the inner drum at or near the inner wall so as to pass from conduit 24 along the inner surface of the drum, thus bringing the drum to the drying temperature. Having heated this surface. the hot gases are caused to pass around the open end of the inner drum and into passageways l7 and through passageways 7 countercurrent to the carbon black passing therethrough. it will be seen that the material being dried is contacted by the hot surfaces of both drums and by the hot combustion gases.

In a more effective embodiment of the apparatus, the outer surface of the outer drum is heated by direct firing. For this purpose, one or more combustion chambers 30 are positioned peripheral to the outer shell of the outer drum. These chambers are equipped with burners 31. Combustion is conducted to heat the outer shell of the outer drum. The hot gases from the chambers are then conducted through conduit 32 into spider 24. These combustion chambers are advantageously fixedly positioned independent of the outer drum.

Any suitable means can be employed for preventing the extensive movement of the inner drum along the longitudinal axis of the outer drum in that embodiment in which the inner drum is unaffixed to the vanes of the outer drum; for example, angles 16 can be employed, these being fastened at their one end to the inner surface of the outer drum at spaced intervals and acting, simultaneously, to form a portion of passageway 17.

There is no critical relationship between the lengths of the two drums. Similarly, there is no critical relationship in respect to the dimensions of the annulus between the drums, it only being desirable that it be of sufficient area to provide adequate area for passageway of the material being dried while imparting to the hot gases velocities conducive to high heat transfer rates.

The apparatus of this invention was constructed for use in drying pelleted carbon black using a l feet-0 inches long outer drum and an inner drum 8 feet-0 inches in length. This inner drum was constructed of 1%; inch stainless steel, was 6 feet-l0 inches in diameter and was positioned within an outer drum having an 8 feet-0 inches diameter. The inner drum was permitted to rotate freely within the outer drum on vanes which had a height slightly less than 7 inches. Eight vanes were positioned around the periphery of the inner wall of the outer drum, the vanes being welded only to the outer drum. The inlet section of the outer drum into which the carbon black was introduced was 2 feet0 inches long. Hot combustion gas was introduced into the inner drum near the carbon black outlet from the drum. This apparatus attained a throughput approximately 10 percent in excess of apparatus of comparable size and combustion gas capacity but employing only a single drying drum.

lt will be evident from the foregoing that various modifications can be made to the invention as disclosed herein. However, such are considered as being within the scope of this invention.

What is claimed is: l. A rotary dryer comprising: a. an outer chamber adapted for rotation about its longitudinal axis, said chamber being adapted at a first end with a port adapted for the introduction of particulate matter and for the discharge of gases and being adapted at a second and opposite end for the discharge of particulate matter; b. an inner chamber unfixedly positioned within said outer chamber, and in spaced relationship therefrom to form an annular passageway therebetween, said inner chamber being supported on vanes positioned in spaced relationship and extending inwardly to said inner chamber from the inner wall of said outer chamber, said inner chamber being closed at a first end positioned proximate the first end of said outer chamber, said inner chamber being open at a second end positioned proximate said second end of said inner chamber, said inner chamber being in open communication with said annular passage, said inner chamber being rotatable independently of said outer chamber;

c. gas introduction means extending into and adapted for discharge into said inner chamber through said second end of said inner chamber; and,

d. means for rotating said outer chamber. 2. The apparatus 0 claim 1 in which said outer chamber 18 adapted with means for heating the outer surface of its wall.

3. The apparatus of claim 2 in which said means for heating comprises a combustion chamber adapted to produce hot gases, said chamber being adapted with conduit means for introduction of hot gases into said fluid introduction means.

4. The apparatus of claim I in which said fluid introduction means comprises a distribution spider.

5. The apparatus of claim 1 in which said outer chamber is adapted with means to restrict the movement of said inner chamber along the longitudinal axis of said outer chamber. 

1. A rotary dryer comprising: a. an outer chamber adapted for rotation about its longitudinal axis, said chamber being adapted at a first end with a port adapted for the introduction of particulate matter and for the discharge of gases and being adapted at a second and opposite end for the discharge of particulate matter; b. an inner chamber unfixedly positioned within said outer chamber, and in spaced relationship therefrom to form an annular passageway therebetween, said inner chamber being supported on vanes positioned in spaced relationship and extending inwardly to said inner chamber from the inner wall of said outer chamber, said inner chamber being closed at a first end positioned proximate the first end of said outer chamber, said inner chamber being open at a second end positioned proximate said second end of said inner chamber, said inner chamber being in open communication with said annular passage, said inner chamber being rotatable independently of said outer chamber; c. gas introduction means extending into and adapted for discharge into said inner chamber through said second end of said inner chamber; and, d. means for rotating said outer chamber.
 2. The apparatus of claim 1 in which said outer chamber is adapted with means for heating the outer surface of its wall.
 3. The apparatus of claim 2 in which said means for heating comprises a combustion chamber adapted to produce hot gases, said chamber being adapted with conduit means for introduction of hot gases into said fluid introduction means.
 4. The apparatus of claim 1 in which said fluid introduction means comprises a distribution spider.
 5. The apparatus of claim 1 in which said outer chamber is adapted with means to restrict the movement of said inner chamber along the longitudinal axis of said outer chamber. 